Spark gap device for lightning arrester

ABSTRACT

A spark gap device for a lightning arrester comprising a first spark gap having a uniform electric field characteristic and a second spark gap connected in parallel with the first spark gap and having a nonuniform electric field characteristic. The spark gaps are disposed in a hermetically sealed housing having an electrically negative gas disposed therein. The resultant spark gap device has a substantially constant sparkover voltage charactetistic since a discharge due to a lightning surge voltage always takes place first across the first spark gap and a discharge due to a low frequency voltage always takes place first across the second spark gap.

United States Patent [191 Yamada et al.

[ 1 Oct. 14, 1975 SPARK GAP DEVICE FOR LIGHTNING ARRESTER 22 Filed: Feb. 1, 1974 211' Appl. No.: 438,766

Related US. Application Data [63] Continuation-impart of Ser. No. 97,999, Dec. 14,

1970, Pat. No. 3,798,498.

[56] References Cited UNITED STATES PATENTS 2,913,626 11/1959 Bislin 315/36 2,958,805 11/1960 Field 313/223 X 3,229,145 l/l966 Jensen 313/223 X 3,414,759 12/1968 Connell et al. 315/36 3,489,949 1/ 1970 Carpenter 315/36 3,496,409 2/ 1970 Connell 315/36 3,515,934 6/1970 Kershaw, Jr. 315/36 3,798,498 3/1974 Yamada et al 315/36 Primary ExaminerPalmer C. Demeo Attorney, Agent, or Firm-Robert E. Burns; Emmanuel J. Lobato; Bruce L. Adams [57] ABSTRACT A spark gap device for a lightning arrester comprising a first spark gap having a uniform electric field characteristic and a second spark gap connected in parallel with the first spark gap and having a nonuniform electric field characteristic. The spark gaps are disposed in a hermetically sealed housing having an electrically negative gas disposed therein. The resultant spark gap device has a substantially constant sparkover voltage charactetistic since a discharge due to a lightning surge voltage always takes place first across the first spark gap and a discharge due to a low frequency voltage always takes place first across the second spark gap.

25 Claims, 10 Drawing Figures 1 1 1 ll/1111111 'II. I l

ull, yea r Oct. 14,1975 Sheet 1 of2 3,912,965

FIG. la

(PRIOR ART) FIG. 2

Fill With Electrically Negative Gas I I0 1000 SPARKOVER TIME IN MICROSECONDS SPARKOVER TIME IN MICROSECONDS FIG 5 US Patent 0a. 14, 1975 Sheet 2 of2 3,912,965

UNIFORM FIELD GAP NONUNIFORM FIELD GAP A ctrode Electrode rfuce Surface SPARK GAP DEVICE FOR LIGHTNING ARRESTER CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of US. Patent application Ser. No. 97,999 filed on Dec. 14, 1970, now US. Pat. No. 3,798,498.

BACKGROUND OF THE INVENTION This invention relates to a spark gap device for a lightning arrester having an improved sparkover voltage characteristic.

With the recent progress in the technology of extrasuperhigh voltage transmission, the lightning arrester has begun to have more chance to sparkover low frequency wave surge (switching surge) voltages derived from the opening or closing of a line than does the system lightning arrester which has heretofore been used. Therefore, the recent spark gap for a lightning arrester for extra-superhigh frequency voltage is required to have a flat sparkover characteristic exhibiting a substantially constant sparkover voltage with respect to various abnormal voltages within a wide frequency range covering from switching surges having a rise time of almost commercial frequency to lightning surges having an abrupt rise time of about 1 us.

The typical gap device for an arrester is provided therein with air or nitrogen gas as an arc quenching medium. On the other hand, it has been known that the use of an electrically negative gas such as an SF gas which is extremely superior in arc quenching ability to those previously used can realize a spark gap device not only excellent in power follow current interrupting capacity but also improved in the sparkover voltage characteristic with the polluted surface of an insulator and corona characteristic. The spark gap device employing an SF gas or the like, however, has not yet been put in practical use. This is partly because the sparkover characteristic of the gap in an atmosphere of an electrically negative gas greatly differs from that in an atmosphere of air or nitrogen gas.

FIG. la illustrates the sparkover voltage characteristics of the uniform field gap shown in FIG. lb and the nonuniform field gap shown in FIG. 10 with respect to sparkover time, which will hereinafter be referred to as the V-t characteristic. More specifically, curve I in FIG. 1a shows the V-t characteristic across the uniform field gap if FIG. lb where d 2r. It is easily understood that the discharge voltage is substantially constant with respect to the wide range of sparkover time and that the dispersion of the sparkover voltage is very large with respect to the voltage such as a slow wave voltage or a switching surge of which intensity varies very slowly the electric field intensity in the uniform electric field can be defined to be equal to or more than 200 kV/cqm at the electrode surface when discharging. Above 200kV/cm, the dispersion in discharge voltage is very small. Curve II in FIG. 1a shows the V-t characteristic across the nonuniform field gap of FIG. where d' 2r'. The curve II shows that the dispersion of the sparkover voltage with respect to the slow wave voltage (switching surge) is small. But in the case of steep front impulse sparkover, the sparkover voltage is very high.

Although the sparkover characteristics as above described can be observed also in an air or a nitrogen gas atmosphere, they are conspicuous particularly in electrically negative gases such as SF having a powerful affinity for electrons. Therefore, in the case where the electrically negative gases are used in combination with a single spark gap, it has been extremely difficult, even when the electric field distribution of the gap is adjustable, to obtain a desired sparkover characteristic exhibiting a flat curve throughout the operative frequency range and a small dispersion of the discharge voltage within the range of the slowwave voltage.

The main reason that the electrically negative gases, though they are an excellent arc quenching medium, have not been employed in the spark gap device for lightning arresters is derived from the fact that the ion chips and the like which are useful in the air or nitrogen gas atmosphere in improving the sparkover characteristic are useless in the atmosphere of electrically negative gases.

When the electrically negative gas such as SF gas is employed as an arc quenching medium in the spark gap device, the gap distance itself can be made very short owing to the excellent insulating ability of the electrically negative gas used. Such a spark gap device, however, is disadvantageous in that the sparkover often takes place only along the surface of the arc quenching plate because the distance between the electrodes is shortened. This has resulted in deterioration of sparkover characteristic of the whole spark gap device. In addition, when the sparkover takes place across the spark gap, the deterioration of the surface of the arc quenching plate will result.

Furthermore, if an arc driving coil is disposed close to the arc quenching plate, the electric field established by the driving coil is concentrated at one portion of the surface of the arc quenching plate. This causes the surface insulation to easily break down.

SUMMARY OF THE INVENTION Accordingly, a chief object of the invention is to provide a spark gap device exhibiting a flat V-t characteristic and having an excellent sparkover characteristic small in dispersion.

Another object of the invention is to provide a spark gap device exhibiting a flat V-t characteristic and having an excellent sparkover characteristic small in dispersion when disposed in an atmosphere of electrically negative gasses such as an SF gas.

Another object of the invention is to provide a spark gap device wherein the arc generated across either of the round electrodes having therebetween a uniform field or the sharp electrodes having therebetween a nonuniform field is directly driven to the driving electrodes from the round electrodes without passing through the sharp electrodes or from the sharp electrodes.

Still another boject of the invention is to provide a spark gap device wherein surface insulation breakdown can hardly take place at that portion of the arc quenching-plates facing the spark gap even when a narrow spark gap is employed owing to the use of an electrically negative gas.

The invention accomplishes these objects by the provision of a spark gap device comprising a uniform field gap having a uniform electric field distribution and a nonuniform field gap having a nonuniform field distribution connected field'gap having a nonuniform field distribution connected in parallel with each other and disposed in an atmosphere of electrically negative gas.

The round electrodes forming the spark gap having the uniform field distribution and the sharp electrodes forming the spark gap having the nonuniform field dis tribution are disposed in superposed relationship with each other to be mounted on each of a common electrode mounting rods separately and rotatably. In addition, recessed portions are formed on that portion of the arc quenching plate facing the spark gaps for the purpose of substantially extending the surface insula tion distances.

According to the invention the spark gap device for a lightning arrester comprises a spark gap having a uni form electric field and a spark gap having a nonuniform electric field connected in parallel with each other. Wherein the spark gap having the uniform electric field always discharges first in response to an impulse voltage input and the spark gap having the nonuniform electric field always discharges first in response to a low frequency wave voltage switching surge input.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1a is graph showing the V-t characteristics of the spark gaps shown in FIGS. lb and 10 having uniform field distribution and a nonuniform field distribution;

FIG. 2 is a schematic diagram showing one embodiment of the invention;

FIG. 3 is a graph showing the V-t characteristic of the spark gap device illustrated in FIG. 2;

FIG. 4 is a schematic diagram illustrating another embodiment of the invention;

FIGS. 5 and 6 are schematic diagrams illustrating other embodiments of the invention;

FIG. 7 is an enlarged plan view of the main portion of the device shown in FIG. 6; and

FIG. 8 is a sectional view taken along the line VIII- -VIII of FIG. 7.

Throughout several Figures the same reference numerals designate the identical or corresponding components.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing and in particular to FIG. 2 thereof, the spark gap device of the present invention generally designated by the reference numeral 10 comprises a uniform electric field distribution gap 12 and a nonuniform electric field distribution gap 14 connected in parallel and both disposed in a hermitically sealed housing 1 such as a porcelain tube having an electrically negative gas 2 therein. It is recalled that the uniform field distribution gap 12 as first shown in FIG. 1b has the sparkover characteristic as illustrated by the curve I in FIG. 1a, while the nonuniform field distribution gap 14 as first shown in FIG. 10 has the sparkover characteristic as illustrated by the curve II in FIG. 1a. Therefore, when these two types of gaps are used in combination as shown in FIG. 2, the resultant sparkover characteristic of the spark gap device 10 becomes as shown in FIG. 3. This is because the sparkover characteristic is determined by the spark gap exhibiting the lower sparkover voltage characteristic for the respective sparkover time. Therefore, it is easily understood that there is the combination of the gap distances preferable for the lightning arrester. This is accomplished by selecting the gap distances of the uniform and nonuniform gaps l2 and 14 so that the sparkover due to a low frequency voltage or a switching surge, the magnitude of which varies very slowly, always takes place across the nonuniform field distribution gap 14, and that the sparkover due to the lightning surge voltage always takes place across the uniform field distribution gap 12. In other words, the spark gap 12 discharges when the voltage in an impulse voltage region is applied, while the spark gap 14 discharges when the voltage in a low frequency voltage region is applied. The spark gap device 10 having a combination of the gap distances thus determined exhibits a V-t characteristic as illustrated in FIG. 3. It is seen from the characteristic curve that the sparkover voltage is substantially constant throughout various sparkover times and that the dispersion of ac. voltage is restrained to be very small. In other words, there is provided a sparkover characteristic preferable for lightning arresters.

Referring now to FIG. 4 wherein a combination of the spark gap device 10 shown in FIG. 2 and the conventional spark gap device of the auxiliary gap type is shown disposed in a hermetically sealed housing 1 such as a porcelain tube having an electrically negative gas 2 therein. It is seen that the spark gap device 10 of the invention comprising the uniform and nonuniform gaps 12 and 14 respectively is used as an auxiliary gap device. The auxiliary gap device 10 is connected through an impedance 16 to a junction 18 formed between two main gaps 20 and 22 shunted by shunting elements 24 and 26 respectively. As is well known, as understood from the V-t curves of the main gaps 20 and 22 and the auxiliary gaps l2 and 14, the sparkover voltage due to the lightning surge voltage always exhibits a higher value than that due to the low frequency voltage, and if an abnormal voltage is applied across terminals 28 and 30, the auxiliary gaps l2 and 14 discharge at first to apply a massive overvoltage across the main gap 20 leading to a discharge of the gap 20 without any delay. Therefore, the main gap 22 discharges in succession to the discharge of the gap 20.

Thus, the resultant sparkover characteristic of the whole device depends upon the sparkover characteristic of the auxiliary gap device 10. Consequently, when the spark gap device employs a combined gap such as the spark gap device 10 illustrated in FIG. 2 as an auxiliary gap, there is provided a spark gap device having a desirable sparkover characteristic as shown in FIG. 3 because of the same resson as in the case of the gap device 10 shown in FIG. 2.

The invention has been described in terms of a spark gap device wherein the single spark gap is replaced by the combined spark gap having uniform and nonuniform field distribution gaps in the electrically negative gases such as an SF gas in order to improve the sparkover characteristic. It is, however, to be understood that the invention is also very useful for obtaining a spark gap device exhibiting a low impact ratio and a dispersion low in sparkover voltage because, even in an atmosphere of air or nitrogen gas, the sparkover characteristic becomes that shown in FIG. 3 when the pressure is higher than the atmospheric pressure. FIG. 5 ill'ustrates another embodiment of the invention concerning the disposition of the gap electrodes in a hermetically sealed housing 2 such as a porcelain tube having an electrically negative gas 2 therein. In FIG. 5, it is seen that the spark gap device 10 for lightning arresters comprises an arc quenching plate 32 provided thereon with driving coils 34 for magnetically driving the generated arc. On the surface of the arc quenching plate 32, there are disposed two pairs of are generating electrodes 36 and 38 defining therebetween a uniform field gap 12 and a nonuniform field gap 14 respectively, and a pair of driving electrodes 40. A characteristic elemefnt 42 is connected in series to the gaps 12 and 14.

The spark gaps l2 and 14 forming therebetween a uniform and a nonuniform electric field respectively has a similar sparkover characteristic to those illustrated in FIG. 2 More specifically, the spark gap 12 has a sparkover characteristic as shown by the curve I in FIG. 1a wherein thesparkover characteristic is flat and the dispersion. of the discharge is small within the impulse sparkover region, while the spark gap 14 has a sparkover characteristic as shown by the curve II in FIG. 1a wherein the sparkover characteristic is extremely high at the left-side or high in impulse ratio and small in discharge dispersion within the low frequency voltage sparkoverv region (or switching surge voltage region). Consequently,.according to the lightning arrestershown in FIG. 5, the impulse sparkover takes place across the gap electrodes 36 while the low frequency voltage sparkover takes place across the electrode 38. This enables the sparkover characteristic to 'beflat and small in dispersion as shown in FIG. 3. The

to extend the arc across the gap electrodes 36 by the driving electrodes 40 having .a wide gap therebetween. This is because the are generated across the gap electrodes 36 is at first transferred to-the sparking electrodes 3 8 and, in turn, to the driving electrodes 40, while the arc generated across the sparking electrodes 38 is immediately transferred to the driving electrodes 40. r

FIGS. 6 to 8 inclusive illustrate the spark gap device effected improvements on the spark gap device illustrated in FIG. 5. i

In these Figures, it is seen that the spark gap device 10 of the invention is disposed in a hermetically sealed housing 1.such as aporcelain tube having an electrically negative gas 2 therein and comprises an arc quenching plate 32 having disposed on its surface a pair of are generating electrodes 36 forming therebetween a uniform field distribution gap 12 and a pair of are generating electrodes 38 forming therebetween a nonuniform field distribution gap 14 in superposed relationship with each other. The electrodes 36 and 38 are in the form of discs having ec centric through holes 70 and 72 respectively for the purpose which will become apparent later. In order-to electrically connect both the electrodes .36 and 38 to eachother and to driving coil 34, a lead plate 42 is interposed between the driving electrodes 40, the arc generating electrodes 36 and the arc quenching plate 32. It is to be noted that the coil 3 4 is adapted to exhibit an electric potential different from that of at least one of the electrodes 36 and 38 or to exhibit an electric potential substantially equal to thatof metallic electrode holding members 54. As is apparent from FIGS. 7 and 8, the direction in which the arc generating electrodes 36 and 38 oppose the driving electrodes 40 is perpendicular to the direction in which the arcgenerating electrodes 36 and 38 are aligned.

. In order to prevent the generated are from passing through the lead plate 42, a recessed portion 44 is formedon the lead plate 42 (FIGS. 6 and 7) at that portion thereof between both the arc generating electrodes 36 and 38 and the driving electrode 40 to oppose each other.

In FIG. 8, it is seen that the spark gap device comprises an arc quenching plate 46 disposed opposingly to the arc quenching plate 32 to sandwich therebetween the arc generating electrodes 36 and 38. The arc quenching plates 32 and 46 are provided on their opposing surfaces with two pairs of recesses 48 and 50 respectively. Each of the recesses 48 formed on the arc quenching plate 32 is filled with a filling metal 52 to hold therein an electrode holding rod 54. The recesses 50 formed on the arc quenching plate 46 serve to accept and hold the heads 56 of the rods 54.

It is also seen that recessed portions 58 and 60 are formed on those portions of the arc quenching plates 32 and 46 facing each other and between the electrodes 36 and 38 respectively.

To hold the various components in their predetermined positions, both the end portions of the arc quenching plates 32 and 46 are provided with through holes 62 and 64 respectively through which screws 66 extend to fix both the arc quenching plate 32 and 46. The screw 66 has on its one end a head, and on the other end a screw threaded portion to which a nut 68 is to fit.

Preferably, the arc quenching plates 32 and 46 are made of acetal resin and the electrodes 36 and 38 are made of graphite. The electrode holding screws 54 are made of suitable metal such as brass or iron, and the screws 66 are made of any suitable insulating material high in mechanical strength such as acetal resin.

When a surge voltage is applied to the spark gap device shown in FIGS. 6 to 8 to produce an arc across any one of the are generating electrodes 36 or 38, the generated arc is transferred to the driving electrodes 40 due to the magnetic field established by the driving coils 34, thereby to expand and quench the arc generated across the electrode 36 or 38.

Comparing the operation of the device in FIGS. 6 to 8 with that of the device in FIG. 5, it is easily understood that the spark gap device illustrated in FIGS. 6 to 8 has several advantages. For example, with the device shown in these Figures, because the generated arc is immediately transferred to the driving electrodes 40 to be expanded therebetween, the arc quenching operation is rapidly achieved, and because the magnetic field is of a constant strength for either of the are generating electrodes, a quite steady interruption is achieved without any adverse change in sparkover characteristic of the device in either case of the are generated across the round electrodes 36 having a uniform field or the sharp electrodes 38 having a nonuniform field.

The assembling operation of the spark gap device shown in FIGS. 6 to 8 and the adjusting operation of the gap distances of the uniform and nonuniform electric field distribution gaps 12,and 14 are performed in the following manner:

Referring to FIG. 8, a lead plate 42 is first placed on the arc quenching plate 32, and then, the round electrodes 36 having a uniform field and the sharp electrodes 38 having a nonuniform field in the named order. The electrode holding rods 54 are inserted and screwedinto the filling metals 52 so as to loosely extend through the bores 70, 72 and 74 formed on the sharp electrodes having a nonuniform field 38, the round electrodes 36 having a uniform field and the lead plate 42 respectively.

The adjustment of the gap distances is performed at this step of assembly. More specifically, the round and the sharp electrodes 36 and 38 are rotated independently of one another about the electrode holding rods 54 so that the gap distances therebetween provide such a combination that the discharges due to slow wave voltages are always performed across the nonuniform spark gap 14, while the discharges due to impulse voltages take place across the uniform spark gap 12.

After the adjustment of the gap distances has been completed, the electrode holding rods 54 are firmly screwed into the filling metals 52 to fix both the electrodes 36 and 38. After that, the arc quenching plate 46 is placed on the assemblage so that the recesses 50 formed on the inner surface thereof snugly receive the respective heads 56 of the electrode holding rods 54. In order to fixedly attach the arc quenching plate 46 to the assemblage, the elongated screws 66 are inserted to the bores 64 and 62 formed on the arc quenching plates 46 and 32 respectively and fastened by the nuts 68.

As easily understood from the foregoing description taken in conjunction with FIGS. 7 and 8, because each of the round and sharp electrodes 36 and 38 having the uniform and nonuniform fields respectively is arranged in the form of a disc, and because the holding rods 54 about which the electrodes are to be turned upon adjusting the gap distances extend eccentrically through the discs, the machining of the electrodes can be of a very high degree of accuracy and the adjustment of the gap distances can be achieved very easily just by turning the electrodes which are eccentrically rotatable discs. This leads to an extremely stable sparkover characteristic.

In addition, the driving electrodes 40 themselves can be designed to be in any preferable structure, disposition and shape which are most preferable for extending and quenching the generated are because the discharge takes place irrespective of the driving electrodes 40.

Further, according to the invention, the arc generating electrodes 36 and 38 are mounted by the metallic member for modulating the electric field (the electrode holding rods 54 are utilized in this embodiment) and the recessed portions 58 and 60 are formed on that portion of the arc quenching plate 32 and 46 facing the spark gaps formed between the electrodes 36 and 38. Therefore, the electric field along the surface of the arc quenching plates is prevented from being partly concentrated owing to the presence of the electrode holding rods 54 which serve as the metallic member for modulating the concentration of the electric field as well as to the presence of the recessed portions on the arc quenching plates.

Therefore, with the arrangement as above described, the breakdown voltage of the surface of the arc quenching plate can be increased without effecting any change in the shape or without increasing dimensions of the electrodes or the spark gaps. Besides, because the surface distance is substantially increased, there is no fear that the sparkover takes place along the surface of the arc quenching plate even when the arc quenching plates are deteriorated due to the discharge across the gaps.

Although the invention has been described only in terms of a single embodiment of a spark gap device for a lightning arrester, it is to be understood that the invention is also applicable to other electric devices employing spark gaps.

What we claim is:

1. A spark gap device for a lightning arrester comprising: a pair of arc quenching plates, a pair of spaced apart metal fillings disposed on one side of one arc quenching plate at a predetermined distance from each other, a pair of metallic electrode holding members attached to said filling metals, means defining a pair of recesses on one side of the other are quenching plate each receiving one end portion of one of said metallic electrode holding members, means defining a first spark gap comprising a pair of spaced apart electrodes and having a uniform electric field characteristic and means eccentrically mounting each electrode on one of said metallic electrode holding members for rotation thereon, means defining a second spark gap comprising a pair of electrodes and having a nonuniform electric field characteristic and means eccentrically mounting each electrode on one of said metallic electrode holding members for rotation thereon and superposed on said first mentioned electrodes, a hermetically sealed housing made of porcelain for commonly disposing said first and second spark gaps in an atmosphere of electrically negative gas, a first are driving coil disposed on the opposite side of said one are quenching plate having an electric potential substantially equal to that of one of said metallic electrode holding members, a second arc driving coil disposed on the opposite side of said other arc quenching plate having an electric potential substantially equal to that of the other of said metallic electrode holding members, and means defining recessed portions formed on a portion of each of said are quenching plates disposed between and spaced from said metallic electrode holding members, and means for pressing together said pair of arc quenching plates and the two pair of superposed electrodes therebetween thereby preventing rotational movement of said electrodes.

2. A spark gap device for a lightning arrester comprising: means defining a first spark gap having a uniform electric field characteristic; means defining a second spark gap connected in parallel with said first spark gap having a nonuniform electric field characteristic; a pair of driving electrodes disposed in parallel with each of said first and second spark gaps; means disposing said driving electrodes and said first and second spark gaps in an atmosphere of electrically negative gas, the gap distances of said first and second spark gaps being selected so that the discharge due to the lightning surge voltage always takes place across said first spark gap and that the discharge due to the slow wave voltage always takes place across said second spark gap.

3. A spark gap device according to claim 2, wherein said means defining said first spark gap includes a first pair of electrodes and said means defining said second spark gap includes a second pair of electrodes.

4. A spark gap device according to claim 3, further comprising driving means for driving the are between said first and second pair of electrodes to said pair of driving electrodes.

5. A spark gap device as claimed in claim 3, comprising means for eccentrically supporting said first and second pairs of electrodes to rotate independently for independent adjustment of spark gap distances, and wherein said first and second pairs of electrodes are substantially discal.

6. A spark gap device as claimed in claim 3, wherein each of said driving electrodes is configured such that the gap distance between the portions of said driving electrodes furthest from said first and second pairs of spark gaps is greater than the gap distance between the portions of said driving electrodes closest to said first and second pairs of spark gaps.

7. A spark gap device as claimed in claim 3, further comprising at least one are quenching member for supporting said electrodes, a metallic member disposed within said are quenching member and, exhibiting an electric potential equal to that of said electrodes, means defining a recess in the other side of said arc quenching member disposed between and spaced from said first and second pair of electrodes and wherein said driving means includes coil means disposed on one side of said are quenching member and having an electric potential different from at least one of said electrodes.

8. A spark gap device as claimed in claim 3, wherein said first and second pairs of electrodes are disposed in a superposed relationship and mounting means for mounting said superposed electrodes so that the longitudinal axis of said superpooed electrodes is substantially perpendicular to the plane of said driving electrodes.

9. A spark gap device as claimed in claim 3, comprising a pair of arc quenching plates, means mounting therebetween said pairs of electrodes and said are driving electrodes, each of said are quenching plates having means therein defining a recessed portion between and spaced from said first and second pairs of electrodes.

10. A spark gap device according to claim 2, wherein said means disposing said gaps in an atmosphere of electrically negative gas comprises a hermetically sealed housing made of porcelain.

11. A spark gap device for a lightning arrester comprising: means defining at least one main spark gap connected in series with each other; at least one auxiliary spark gap connected in parallel with one main spark gap and each auxiliary spark gap comprising means defining a first spark gap having a uniform electric fireld characteristic and means defining a second spark gap connected in parallel with said first spark gap and having a nonuniform electric field characteristic; and means disposing said main spark gaps and said first and second spark gaps in an atmosphere of electrically negative gas; wherein the gap distances of said first and second spark gaps being selected so that the discharge due to the lightning surge voltage always takes place across said first spark gap and that the discharge due to the slow wave voltage always takes place across said second spark gap.

12. A spark gap device according to claim 11, wherein said means disposing said gaps in an atmosphere of electrically negative gas comprises a hermetically sealed housing made of porcelain.

13. A spark gap device according to claim 11, wherein said means defining said first spark gap includes a first pair of electrodes and said means defining said second spark gap includes a second pair of electrodes.

14. A spark gap device according to claim 13, further comprising driving means for driving the are between said first and second pair of electrodes to said main spark gap.

15. A spark gap device according to claim 11, wherein comprising a plurality of main spark gaps and wherein one of said at least one auxiliary spark gaps is connected in parallel with one of said main spark gaps.

16. A spark gap device for a lightning arrester comprising: means defining a first spark gap receptive thereacrossduring use of the device of an input voltage having a risetime and said first spark gap having a sparkover voltage-risetime characteristic wherein the sparkover voltage is equal to 'a predetermined substantially constant value for input voltage risetimes greater than a predetermined value and a value no less than said predetermined substantially constant value for risetimes less than said predetermined value; means defining a second spark gap receptive thereacross during use of the device of an input voltage having a risetime and connected in parallel with said first spark gap and having another sparkover voltage-risetime characteristic wherein the sparkover voltage is equal to said predetermined substantially constant value for input voltage risetimes less than said predetermined value and no less than said predetermined substantially constant value for risetimes greater than said predetermined value; and a hermetically sealed housing made of porcelain for commonly disposing said first and second spark gaps in an atmoshpere of electrically negative gas; whereby the first spark-gap always sparks over first for input voltage risetimes greater than said predetermined value and the second spark-gap always sparks over first for input voltage risetimes less than said predetermined value and thereby said parallel combination of said first spark gap and said second spark gap imparts to the spark gap device a substantially constant sparkover voltage-risetime characteristic.

17. A spark gap device according to claim 16, wherein said means defining said first spark gap includes a first pair of electrodes having a geometric shape effective to impart said sparkover voltagerisetime characteristic to said first spark gap and said means defining said second spark gap includes a second pair of electrodes having a geometric shape effective to impart said another sparkover voltage-risetime characteristic to said second spark gap.

18. A spark gap device for a lightning arrester comprising: means defining at least one series connected main spark gap receptive thereacross during use of the device of an input voltage having a risetime and having a sparkover voltage-risetime characteristic wherein the sparkover voltage is greater than a first predetermined value over the range of operative input voltage risetimes; means defining at least one auxiliary spark gap receptive thereacross during use of the device of an input voltage having a risetime and connected in parallel with said main spark gap and comprising means defining a first spark gap having a sparkover voltagerisetime characteristic wherein the sparkover voltage is equal to a predetermined substantially constant value less than said first predetermined value for input voltage risetimes greater than a second predetermined value and a value no less than said predetermined substantially constant value for risetimes less than said second predetermined value and means defining a second spark gap connected in parallel with said first spark gap and having another voltage-risetime characteristic wherein the sparkover voltage is equal to said predetermined substantially constant value for imput voltage risetimes less than said second predetermined value and a value no less than said predetermined substantially constant value for risetimes greater than said second predetermined value; and means disposing said main spark gaps and said first and second spark gaps in an atmosphere of electrically negative gas; whereby the first spark-gap always sparks over first for input voltage risetimes greater than said second predetermined value and the second spark-gap always sparks over first for input voltage risetimes less than said second predetermined value and thereby the parallel combination of said first and second spark gaps imparts to said auxiliary spark gap a substantially constant sparkover voltage-risetime characteristic and the parallel combination of said auxiliary spark gap and said main spark gap imparts to the spark gap device substantially constant sparkover voltage-risetime characteristic.

19. A spark gap device according to claim 18, wherein said means disposing said gaps in an atmosphere of electrically negative gas comprises a hermetically sealed housing made of porcelain.

20. A spark gap device according to claim 18, comprising a plurality of series connected main spark gaps and wherein each of said at least one auxiliary spark gaps are connected in parallel with one of said main spark gaps.

21. A spark gap device according to claim 20, wherein said means disposing said gaps in an atmosphere of electrically negative gas comprises a hermetically sealed housing made of porcelain.

22. A spark gap device according to claim 18, wherein said means defining said main spark gap includes one pair of spaced-apart electrodes, said means defining said first spark gap comprises a first pair of spaced-apart electrodes and said means defining said second spark gap connected in parallel with said first spark gap comprises a second pair of spaced-apart electrodes and further comprising mounting means for mounting said first pair of electrodes and said second pair of electrodes in superposed abutting relationship and including means for mounting each pair of superposed electrodes for independent adjustment of said first and second spark gaps.

23. A spark gap device according to claim 22, wherein each of said first pair of electrodes comprise a disc having two main sides and a circumferential side having a bluntly arcuate cross-section and each of said second pair of electrodes comprises a disc having two main sides and a circumferential side having a pointed cross-section.

24. A spark gap device according to claim 23, wherein said mounting means comprises two are quenching members for mounting each pair of superposed electrodes and said one pair of electrodes therebetween each of said are quenching members having two main sides opposite one another, the inward side of each having means therein defining a recess disposed at a portion of said inward side spaced from and between each of said two pairs of superposed electrodes for increasing the lateral surface distance along the surface of each of said inward sides between each of said two pairs of superposed electrodes.

25. A spark gap device according to claim 24, wherein said means for mounting said first and second pair of electrodes in superposed abutting relationship comprises two electrically conductive electrode holding members, means for mounting said electrode holding members between said two inward sides of said are quenching members, and means for eccentrically mounting each of said two pairs of superposed electrodes on one of said holding memebers for rotation therein and means for pressing together said arc quenching members and said two pairs of superposed electrodes and said one pair of electrodes therebetween and thereby preventing said two pair of superposed electrodes from rotating. 

1. A spark gap device for a lightning arrester comprising: a pair of arc quenching plates, a pair of spaced apart metal fillings disposed on one side of one arc quenching plate at a predetermined distance from each other, a pair of metallic electrode holding members attached to said filling metals, means defining a pair of recesses on one side of the other arc quenching plate each receiving one end portion of one of said metallic electrode holding members, means defining a first spark gap comprising a pair of spaced apart electrodes and having a uniform electric field characteristic and means eccentrically mounting each electrode on one of said metallic electrode holding members for rotation thereon, means defining a second spark gap comprising a pair of electrodes and having a nonuniform electric field characteristic and means eccentrically mounting each electrode on one of said metallic electrode holding members for rotation thereon and superposed on said first mentioned electrodes, a hermetically sealed housing made of porcelain for commonly disposing said first and second spark gaps in an atmosphere of electrically negative gas, a first arc driving coil disposed on the opposite side of said one arc quenching plate having an electric potential substantially equal to that of one of said metallic electrode holding members, a second arc driving coil disposed on the opposite side of said other arc quenching plate having an electric potential substantially equal to that of the other of said metallic electrode holding members, and means defining recessed portions formed on a portion of each of said arc quenching plates disposed between and spaced from said metallic electrode holding members, and means for pressing together said pair of arc quenching plates and the two pair of superposed electrodes therebetween thereby preventing rotational movement of said electrodes.
 2. A spark gap device for a lightning arrester comprising: means defining a first spark gap having A uniform electric field characteristic; means defining a second spark gap connected in parallel with said first spark gap having a nonuniform electric field characteristic; a pair of driving electrodes disposed in parallel with each of said first and second spark gaps; means disposing said driving electrodes and said first and second spark gaps in an atmosphere of electrically negative gas, the gap distances of said first and second spark gaps being selected so that the discharge due to the lightning surge voltage always takes place across said first spark gap and that the discharge due to the slow wave voltage always takes place across said second spark gap.
 3. A spark gap device according to claim 2, wherein said means defining said first spark gap includes a first pair of electrodes and said means defining said second spark gap includes a second pair of electrodes.
 4. A spark gap device according to claim 3, further comprising driving means for driving the arc between said first and second pair of electrodes to said pair of driving electrodes.
 5. A spark gap device as claimed in claim 3, comprising means for eccentrically supporting said first and second pairs of electrodes to rotate independently for independent adjustment of spark gap distances, and wherein said first and second pairs of electrodes are substantially discal.
 6. A spark gap device as claimed in claim 3, wherein each of said driving electrodes is configured such that the gap distance between the portions of said driving electrodes furthest from said first and second pairs of spark gaps is greater than the gap distance between the portions of said driving electrodes closest to said first and second pairs of spark gaps.
 7. A spark gap device as claimed in claim 3, further comprising at least one arc quenching member for supporting said electrodes, a metallic member disposed within said arc quenching member and, exhibiting an electric potential equal to that of said electrodes, means defining a recess in the other side of said arc quenching member disposed between and spaced from said first and second pair of electrodes and wherein said driving means includes coil means disposed on one side of said arc quenching member and having an electric potential different from at least one of said electrodes.
 8. A spark gap device as claimed in claim 3, wherein said first and second pairs of electrodes are disposed in a superposed relationship and mounting means for mounting said superposed electrodes so that the longitudinal axis of said superpooed electrodes is substantially perpendicular to the plane of said driving electrodes.
 9. A spark gap device as claimed in claim 3, comprising a pair of arc quenching plates, means mounting therebetween said pairs of electrodes and said arc driving electrodes, each of said arc quenching plates having means therein defining a recessed portion between and spaced from said first and second pairs of electrodes.
 10. A spark gap device according to claim 2, wherein said means disposing said gaps in an atmosphere of electrically negative gas comprises a hermetically sealed housing made of porcelain.
 11. A spark gap device for a lightning arrester comprising: means defining at least one main spark gap connected in series with each other; at least one auxiliary spark gap connected in parallel with one main spark gap and each auxiliary spark gap comprising means defining a first spark gap having a uniform electric fireld characteristic and means defining a second spark gap connected in parallel with said first spark gap and having a nonuniform electric field characteristic; and means disposing said main spark gaps and said first and second spark gaps in an atmosphere of electrically negative gas; wherein the gap distances of said first and second spark gaps being selected so that the discharge due to the lightning surge voltage always takes place across said first spark gap and that the discharge due to the slow wave voltage always takes place across said second sparK gap.
 12. A spark gap device according to claim 11, wherein said means disposing said gaps in an atmosphere of electrically negative gas comprises a hermetically sealed housing made of porcelain.
 13. A spark gap device according to claim 11, wherein said means defining said first spark gap includes a first pair of electrodes and said means defining said second spark gap includes a second pair of electrodes.
 14. A spark gap device according to claim 13, further comprising driving means for driving the arc between said first and second pair of electrodes to said main spark gap.
 15. A spark gap device according to claim 11, wherein comprising a plurality of main spark gaps and wherein one of said at least one auxiliary spark gaps is connected in parallel with one of said main spark gaps.
 16. A spark gap device for a lightning arrester comprising: means defining a first spark gap receptive thereacross during use of the device of an input voltage having a risetime and said first spark gap having a sparkover voltage-risetime characteristic wherein the sparkover voltage is equal to a predetermined substantially constant value for input voltage risetimes greater than a predetermined value and a value no less than said predetermined substantially constant value for risetimes less than said predetermined value; means defining a second spark gap receptive thereacross during use of the device of an input voltage having a risetime and connected in parallel with said first spark gap and having another sparkover voltage-risetime characteristic wherein the sparkover voltage is equal to said predetermined substantially constant value for input voltage risetimes less than said predetermined value and no less than said predetermined substantially constant value for risetimes greater than said predetermined value; and a hermetically sealed housing made of porcelain for commonly disposing said first and second spark gaps in an atmoshpere of electrically negative gas; whereby the first spark-gap always sparks over first for input voltage risetimes greater than said predetermined value and the second spark-gap always sparks over first for input voltage risetimes less than said predetermined value and thereby said parallel combination of said first spark gap and said second spark gap imparts to the spark gap device a substantially constant sparkover voltage-risetime characteristic.
 17. A spark gap device according to claim 16, wherein said means defining said first spark gap includes a first pair of electrodes having a geometric shape effective to impart said sparkover voltage-risetime characteristic to said first spark gap and said means defining said second spark gap includes a second pair of electrodes having a geometric shape effective to impart said another sparkover voltage-risetime characteristic to said second spark gap.
 18. A spark gap device for a lightning arrester comprising: means defining at least one series connected main spark gap receptive thereacross during use of the device of an input voltage having a risetime and having a sparkover voltage-risetime characteristic wherein the sparkover voltage is greater than a first predetermined value over the range of operative input voltage risetimes; means defining at least one auxiliary spark gap receptive thereacross during use of the device of an input voltage having a risetime and connected in parallel with said main spark gap and comprising means defining a first spark gap having a sparkover voltage-risetime characteristic wherein the sparkover voltage is equal to a predetermined substantially constant value less than said first predetermined value for input voltage risetimes greater than a second predetermined value and a value no less than said predetermined substantially constant value for risetimes less than said second predetermined value and means defining a second spark gap connected in parallel with said first spark gap and having another voltage-risetime characteristic wherein the sparkover voltage is equal to said predetermined substantially constant value for imput voltage risetimes less than said second predetermined value and a value no less than said predetermined substantially constant value for risetimes greater than said second predetermined value; and means disposing said main spark gaps and said first and second spark gaps in an atmosphere of electrically negative gas; whereby the first spark-gap always sparks over first for input voltage risetimes greater than said second predetermined value and the second spark-gap always sparks over first for input voltage risetimes less than said second predetermined value and thereby the parallel combination of said first and second spark gaps imparts to said auxiliary spark gap a substantially constant sparkover voltage-risetime characteristic and the parallel combination of said auxiliary spark gap and said main spark gap imparts to the spark gap device substantially constant sparkover voltage-risetime characteristic.
 19. A spark gap device according to claim 18, wherein said means disposing said gaps in an atmosphere of electrically negative gas comprises a hermetically sealed housing made of porcelain.
 20. A spark gap device according to claim 18, comprising a plurality of series connected main spark gaps and wherein each of said at least one auxiliary spark gaps are connected in parallel with one of said main spark gaps.
 21. A spark gap device according to claim 20, wherein said means disposing said gaps in an atmosphere of electrically negative gas comprises a hermetically sealed housing made of porcelain.
 22. A spark gap device according to claim 18, wherein said means defining said main spark gap includes one pair of spaced-apart electrodes, said means defining said first spark gap comprises a first pair of spaced-apart electrodes and said means defining said second spark gap connected in parallel with said first spark gap comprises a second pair of spaced-apart electrodes and further comprising mounting means for mounting said first pair of electrodes and said second pair of electrodes in superposed abutting relationship and including means for mounting each pair of superposed electrodes for independent adjustment of said first and second spark gaps.
 23. A spark gap device according to claim 22, wherein each of said first pair of electrodes comprise a disc having two main sides and a circumferential side having a bluntly arcuate cross-section and each of said second pair of electrodes comprises a disc having two main sides and a circumferential side having a pointed cross-section.
 24. A spark gap device according to claim 23, wherein said mounting means comprises two arc quenching members for mounting each pair of superposed electrodes and said one pair of electrodes therebetween each of said arc quenching members having two main sides opposite one another, the inward side of each having means therein defining a recess disposed at a portion of said inward side spaced from and between each of said two pairs of superposed electrodes for increasing the lateral surface distance along the surface of each of said inward sides between each of said two pairs of superposed electrodes.
 25. A spark gap device according to claim 24, wherein said means for mounting said first and second pair of electrodes in superposed abutting relationship comprises two electrically conductive electrode holding members, means for mounting said electrode holding members between said two inward sides of said arc quenching members, and means for eccentrically mounting each of said two pairs of superposed electrodes on one of said holding memebers for rotation therein and means for pressing together said arc quenching members and said two pairs of superposed electrodes and said one pair of electrodes therebetween and thereby preventing said two pair of superposed electrodes from rotating. 